1. Field of the Invention
The invention relates to a shock absorber, comprising a damping element and an air spring, the damping element having a container tube which is connected to a rolling tube of the air spring, the rolling tube being connected via a spring bellows acting as a rolling bellows to an outer tube which is arranged concentrically and such that it can move axially with respect to the rolling tube, the spring bellows and the rolling tube bounding a gas chamber provided with a gas filling under pressure.
2. Description of the Related Art
Shock absorbers of the aforementioned type are used, for example, on a suspension of a driver""s cab on a chassis of a utility vehicle, in order to keep the oscillations introduced into the chassis by the road via the wheel suspensions largely away from the driver""s cab. In this case, the outer tube of the air spring and a piston rod of the damping element are connected to the driver""s cab, and the damping element is connected to the chassis via a fixing component. The action of the air spring depends on the size and the pressure prevailing in the gas chamber, the distance of the outer tube from the rolling tube, and the shape of the rolling profile on the rolling tube.
The solution to the problem of sealing the gas chamber with respect to the atmosphere, by using a O ring between the rolling tube of the air spring and the container tube of the damping element, belongs to the prior art. In order to dissipate the axial component of the gas pressure, acting as a result of the high prestress in the gas chamber, onto the container tube, a design has hitherto been chosen which provides an adapter ring, which can be produced only with high expenditure on production and has to be welded to the container tube. Furthermore, the O ring is arranged in the adapter ring or in the vicinity thereof, which makes the design complicated and more expensive. One contour of the rolling tube is supported axially on the adapter ring, which intercepts the axial forces from the air spring and dissipates them into the container tube. However, the higher the numbers are, the greater becomes the demand for rationalization of the aforementioned support and sealing of the rolling tube on the container tube.
In order to support the rolling tube axially on the container tube and to seal off the rolling tube with respect to the container tube, the present invention proposes dispensing with the costly adapter ring and separating the two functions xe2x80x9csupportxe2x80x9d and xe2x80x9csealingxe2x80x9d physically from each other and replacing them by devices known per se. Since the gas chamber of the air spring is under continuous pressure, it is merely necessary to secure the rolling tube axially with respect to the container tube of the damping element in the direction pointing away from the air spring. For this purpose, the container tube can be provided with integral moldings which the rolling tube strikes with a constriction or with its front end. The integral moldings are preferably indentations having a lug and possibly also a contact shoulder, against which the rolling tube is pressed by the pressure in the air spring. When the shock absorber is installed, the result is therefore a stable positional state for the rolling tube with respect to the container tube of the damping element, as a result of the pressure prevailing continuously in the air spring. Instead of the integral moldings on the container tube, however, there may also be a groove, into which the end of the rolling tube is rolled. Finally, it is also possible nowadays to make an adhesively bonded connection, with or without form-fitting surface configurations on the two tubes.
According to the proposal of the invention, the sealing of the rolling tube with respect to the container tube is performed by an O ring, whose position is determined by a groove in the container tube. This groove is rolled into the container tube and therefore has rounded edges and a surface with low roughness, which are imperative for tightness over the entire lifetime of the sealing element. In the case where the contact shoulder is provided, it is expedient to widen the end region of the rolling tube at the front end slightly conically, corresponding to the shape of the contact shoulder. This makes it easier to mount the rolling tube over the O ring in its groove in the container tube with a low faulty assembly rate in large-scale mass production, since the O ring does not come into contact with the inner edge of the front end.
The present invention has therefore taken as its object the provision of a shock absorber, comprising a damping element and an air spring, in which a rolling tube, as a constituent part of the air spring, can be fixed axially and sealed with respect to a container tube of the damping element in a cost-effective way and with little expenditure on assembly.
According to the invention, the container tube is sealed off with respect to the rolling tube by an O ring. At another point on the container tube, a stop for the rolling tube is arranged in order to dissipate the axial component of the gas pressure acting on the rolling tube.
An exemplary embodiment of an axial fixing with sealing of a rolling tube of an air spring with respect to a container tube of a damping element will be explained by using a drawing.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.